Light combiner and augmented reality device including the same

Abstract

A light combiner combines first light provided by a light source with second light containing an image of an exterior environment and provides the combined light to a user. The light combiner includes a transmissive optical device comprising a first surface on which the first light is incident and a second surface facing the first surface, and branching the first light in a plurality of directions to pass through the second surface, and a holographic optical device on a side of the transmissive optical device facing the second surface and spaced apart from the transmissive optical device. The holographic optical device diffracts light rays branched and transmitted by the transmissive optical device in the plurality of directions, to be respectively focused at a plurality of focal points different from each other and corresponding to the directions, and transmits the second light therethrough to travel toward the plurality of focal points.

What is claimed is: 
     
       1. A light combiner for combining a first light provided from a light source with a second light containing an image of an exterior environment and providing the combined light to a user, the light combiner comprising:
 a transmissive optical device comprising a first surface on which the first light is incident and a second surface facing the first surface, the transmissive optical device branching the first light in a plurality of directions to pass through the second surface; and 
 a holographic optical device provided on a side of the transmissive optical device facing the second surface and spaced apart from the transmissive optical device, 
 wherein the holographic optical device diffracts a plurality of light rays that have been branched in the plurality of directions and transmitted by the transmissive optical device, to be respectively focused at a plurality of focal points different from each other and corresponding to the plurality of directions, and 
 wherein the holographic optical device transmits the second light therethrough so as to travel toward the plurality of focal points. 
 
     
     
       2. The light combiner of  claim 1 , wherein the holographic optical device comprises an interference pattern that diffracts a first incident light emanating from a first reference point, to be focused at a first focal point, the first reference point being fixedly located outside the holographic optical device. 
     
     
       3. The light combiner of  claim 2 , wherein
 the holographic optical device diffracts a second incident light emanating from a second reference point that is different from the first reference point, to be focused at a second focal point that is different from the first focal point, and 
 a diffraction efficiency of the holographic optical device with respect to the second incident light is less than a diffraction efficiency of the holographic optical device with respect to the first incident light. 
 
     
     
       4. The light combiner of  claim 3 , wherein the transmissive optical device comprises a transmissive diffractive optical element that diffracts the first light such that it is branched in the plurality of directions. 
     
     
       5. The light combiner of  claim 4 , wherein the transmissive optical device branches the first light into the plurality of light rays, and
 wherein a first portion of the plurality of light rays corresponds to the first incident light and a second portion of the plurality of light rays corresponds to the second incident light. 
 
     
     
       6. The light combiner of  claim 4 , wherein the transmissive optical device branches the first light such that a difference Δθ between a respective incident angle of each of the plurality of light rays upon the holographic optical device and an incident angle of the first incident light upon the holographic optical device is within a range of −2°≤Δθ≤2°. 
     
     
       7. The light combiner of  claim 1 , wherein the transmissive optical device branches the first light in the plurality of directions with a same intensity of light in each direction of the plurality of directions. 
     
     
       8. The light combiner of  claim 1 , wherein the holographic optical device focuses the plurality of light rays branched in the plurality of directions and transmitted by the transmissive optical device respectively at the plurality of focal points different from each other,
 wherein the plurality of focal points is located on a side of the transmissive optical device facing the first surface of the transmissive optical device, and 
 wherein the holographic optical device transmits the second light to travel toward the plurality of focal points. 
 
     
     
       9. The light combiner of  claim 1 , further comprising a spacer that is provided between the transmissive optical device and the holographic optical device to separate the transmissive optical device from the holographic optical device. 
     
     
       10. The light combiner of  claim 9 , wherein the spacer comprises a transparent substrate that covers the second surface of the transmissive optical device. 
     
     
       11. The light combiner of  claim 9 , wherein the spacer comprises a column that is provided at an edge of the second surface of the transmissive optical device. 
     
     
       12. The light combiner of  claim 11 , wherein an empty space is formed between the transmissive optical device, the holographic optical device, and the spacer. 
     
     
       13. The light combiner of  claim 1 , wherein the transmissive optical device branches the first light such that points of incidence of the plurality of light rays on the holographic optical device form a two-dimensional pattern. 
     
     
       14. An augmented reality device comprising:
 a light source; 
 a spatial light modulator that modulates a first light from the light source; and 
 a light combiner that combines the first light modulated by the spatial light modulator with a second light containing an image of an exterior environment and provides the combined light to a user, 
 wherein the light combiner comprises:
 a transmissive optical device comprising a first surface on which the first light is incident and a second surface facing the first surface, the transmissive optical device branching the first light in a plurality of directions to pass through the second surface; and 
 a holographic optical device provided on a side of the transmissive optical device facing the second surface and spaced apart from the transmissive optical device, 
 
 wherein the holographic optical device diffracts a plurality of light rays that have been branched in the plurality of directions and transmitted by the transmissive optical device, to be respectively focused at a plurality of focal points different from each other and corresponding to the plurality of directions, and 
 wherein the holographic optical device transmits the second light therethrough to travel toward the plurality of focal points. 
 
     
     
       15. The augmented reality device of  claim 14 , wherein the light combiner further comprises a spacer that is provided between the transmissive optical device and the holographic optical device to separate the transmissive optical device from the holographic optical device. 
     
     
       16. The augmented reality device of  claim 14 , further comprising a processor that controls an operation of the spatial light modulator. 
     
     
       17. The augmented reality device of  claim 14 , wherein the holographic optical device comprises an interference pattern that diffracts a first incident light emanating from a first reference point, to be focused at a first focal point. 
     
     
       18. The augmented reality device of  claim 17 , wherein
 the interference pattern diffracts a second incident light emanating from a second reference point that is different from the first reference point, to be focused at a second focal point that is different from the first focal point, and 
 a diffraction efficiency of the holographic optical device with respect to the second incident light is less than a diffraction efficiency of the holographic optical device with respect to the first incident light. 
 
     
     
       19. The augmented reality device of  claim 18 , wherein the transmissive optical device comprises a transmissive diffractive optical element that diffracts the first light such that it is branched in the plurality of directions. 
     
     
       20. The augmented reality device of  claim 19 , wherein the transmissive optical device branches the first light into the plurality of light rays, and
 wherein a first portion of the plurality of light rays corresponds to the first incident light and a second portion of the plurality of light rays corresponds to the second incident light. 
 
     
     
       21. The augmented reality device of  claim 14 , wherein the augmented reality device comprises a wearable device.